Audio-tactile pedestrian push button signalling system

ABSTRACT

An audio-tactile pedestrian signalling system for use in conjunction with traffic control signal installation having a transducer (16) providing audio and tactile signals by means of signal generator (11, 12, 13, 14). The transducer acts as a microphone to provide a feedback signal to an automatic gain control circuit (19) to adjust the signal to noise level ratio with respect to ambient traffic noise.

FIELD OF INVENTION

This invention relates to audio-tactile pedestrian push-buttonsignalling systems for use in conjunction with traffic control signalinstallations.

BACKGROUND ART

An audio-tactile traffic signalling system provides combined audible andtactile signals to supplement the normal pedestrian light signals atcontrolled pedestrian crossings. Two types of audio-tactile signals areprovided:

(a) a locating signal which enables the visually handicapped person tolocate the push-button assembly and register a demand. This signal iscontinuously emitted except when the associated pedestrian light signalis green,

(b) a crossing signal which is emitted only when the associatedpedestrian light signal is green.

The tranducer for the audio-tactile signal is located within thepush-button assembly and acts on the front surface of the push-buttonhousing. The associated electronic equipment to drive the tranducer iscontained in a separate housing remote from the push-button assembly,for example, adjacent to the traffic lights. The remote driver unit orhousing is hard-wired to the transducer in the push-button assembly.

The audible locating signal as defined by the Department of Main Road ofNew South Wales, Australia specification ATS/2 has the followingoperational characteristics:

(a) a fundamental frequency within the range 900 Hz to 1100 Hz;

(b) a spectral bandwidth extending to at least 5 kHz;

(c) a rectangular waveform with a rectangular modulation envelope ofbetween 20 ms and 30 ms duration;

(d) a pulse repetition frequency within the range of 0.5 to 0.6 Hz;

(e) an output sound pressure level which is automatically adjusted tomaintain a constant relationship with the instantaneous A-weightedambient noise level over the range 35 to 75 dB (A); and

(f) fixed upper and lower output sound pressure levels which aremaintained when the ambient noise is outside the range specified in (e)above.

In order to comply with requirement (e), a microphone is mounted withinthe remote driver unit or housing to monitor the ambient noise level andto provide a suitable control signal.

The audible crossing signal as defined by the above specification ATS/2has two separate stages:

(a) an initial transition stage comprising a single pulse of a constantamplitude square wave having a frequency changing exponentially from 2kHz to 500 Hz with a time constant of 50 ms; and

(b) a second stage having the following operational characteristics:

(i) a fundamental frequency of between 400 Hz and 600 Hz;

(ii) a spectral bandwidth extending to at least 5 kHz;

(iii) a sinusoidal waveform with an amplitude decaying exponentiallywith a time constant of 50 ms; and

(iv) a pulse repetition frequency within the range 8 Hz to 10 Hz.

The tactile signal generated on the front of the push button assemblyhousing is defined by specification ATS/2 as follows:

(a) the area over which the tactile signal is generated shall be atleast 30 mm diameter located immediately above the push-button switch,using a pedestrian push-button switch assembly complying withspecification No. PB/5.

(b) the tactile signal shall have a sinusoidal waveform with a frequencylying between 100 Hz and 175 Hz.

(c) the tactile signal shall be in-phase with the audible signalsspecified under Clauses 3.2 and 3.3. The signal shall comprise anintegral number of cycles (between 3 and 8) commencing and finishing ona zero crossing, with a duration of not less than 30 milliseconds andperiodicity corresponding to the audible signal.

(d) the tactile signal output shall have a peak acceleration exceeding 1g (9.81 m/s²). This will necessitate an output voltage in the range 8 to11 V peak-to-peak, depending upon frequency, for the nominal sensitivityof the transducer specified in FIG. 2.

The remote driver unit or housing contains two isolating transformersconnected to:

(a) a nominal 240 volt AC mains supply, and,

(b) the nominal 240 volt AC active feed to the associated pedestriangreen signal lamps,

for operation of the audio-tactile tranducer as well as the associatedelectronic circuits.

Although the applicant's prior art audio-tactile traffic signallingsystem of the kind described above has achieved wide commercialacceptance, there is a need for an improved system which is simpler inconstructional detail and cheaper to produce.

DISCLOSURE OF INVENTION

An audio-tactile pedestrian push-button signalling system according tothe present invention includes a housing, signal generator means havingan Automatic Gain Control circuit within the housing, a tranducer withinthe housing operative under the control of the signal generating meansto produce pre-determined audio and tactile signals, said transducerbeing adapted to act as a responsive microphone so as to provide afeedback signal to the Automatic Gain Control circuit for adjusting thesignal to noise level ratio with respect to ambient traffic noise.

The mounting of the signal generator means and the transducer within thepedestrian push-button housing obviates the need for an additionaldriver unit or housing as is required by prior art systems. Linetranformers may be mounted within the associated pedestrian signallanterns which would be advantageous in that it would segregate the lowvoltage and extra low voltage levels.

In a preferred form of the invention, the push-button housing andactuator are manufactured by injection moulding techniques from highgrade engineering plastics such as polycarbonate or glass-filled nylon.The use of an injected moulded housing obviates the need for machining,degreasing and painting as is the case with the current aluminium casthousing.

The signal generator means incorporates thick film hybrid microelectronics which reduces the area required to house the electroniccircuitry so it may be located within the pedestrian push-button ratherthan in a separate driver unit housing.

A compact signal tranducer is designed to produce the correct audibleand tactile signals at the appropriate levels. The transducer also actsas a responsive microphone and is capable of providing the requiredfeed-back to operate the Automatic Gain Control circuit so as to adjustthe signal to noise level ratio with respect to ambient traffic noise.Such a tranducer eliminates the need for the microphone used in presentaudio-tactile signalling systems.

The audio-tactile signal generator system is driven by a single linetransformer which is mounted within the associated pedestrian signallantern. The input to the signal generator is so arranged, and the linetransformer so switched, to differentiate via half and full wavealternating current switching in order to produce the locating andcrossing signals with full failsafe backup.

The audio-tactile signal generator also produces a visual indication tothe pedestrian, to advise that the button has been previously pressedand the crossing signal (as movement) will be serviced by the controllerin cyclic order.

BRIEF DESCRIPTION OF THE DRAWING

In order that the invention may be more readily understood and put intopractical effect, reference will now be made to the accompanying drawingwhich is a schematic diagram of a signal system for an audio-tactilepedestrian push-button according to an embodiment of the invention.

BEST MODE OF CARRYING OUT THE INVENTION

The signalling system shown in the drawing includes a main timingnetwork 10 which controls four separate tone generators namely:

(a) WALK tone generator 11 which is adapted to produce a 500 Hz decayingsinewave,

(b) DON'T WALK tone generator 12 which is adapted to produce 32 cyclesof a 1 kHz square wave,

(c) CHANGE tone generator 13 which is adapted to produce a square waveburst starting at about 2 kHz and dropping to 500 Hz over a 50millisecond period,

(d) TACTILE tone generator 14 which is adapted to produce 4 cycles of a128 Hz sinewave.

The output of each of the tone generators 11,12,13 and 14 is applied topower amplifier 15 which drives the transducer 16. The main power supplyunit 17 is remote from the transducer 16, being either at the top of thetraffic light pole (not shown) or at the main control box (also notshown) for the system.

The power supply unit 17 provides an extra low A.C. votage which is halfwave during the DON'T WALK mode and full wave during the WALK mode.Thus, only two wires are needed to power and control the system. Thelocal power supply unit 18 within the pedestrian push-button housingrectifies the A.C. signal from the power supply unit 17 to provide theD.C. voltages required. The local power supply unit 18 also decodes thefull wave/half wave signal to provide the WALK and DON'T WALK signals tothe main timing network 10.

The sound transducer 16 is constituted by the circular aluminium platenormally used in the push-button assembly as the direction arrowindicator. The transducer 16 is vibrated by a loudspeaker style magnetand voice coil assembly. The transducer 16 is also used as themicrophone for the automatic volume control in the DON'T WALK mode.

The power amplifier 15 has an output DISABLE control to allow thetransducer 16 to be used as the microphone during the time betweenpulses in the DON'T WALK signal. The microphone output of the transducer16 is applied to amplifier/rectifier 19 to give a D.C. signal whichautomatically controls the gain of the DON'T WALK signal. The network 10has a disable control to prevent it from being swamped by the poweramplifier when it is active.

The tone generators 11,12,13 and 14 are controlled by the main timingcircuit 10 so that in the DON'T WALK mode the tactile tone is repeatedevery 2 seconds followed immediately by the DON'T WALK tone burst toprovide an audible locating signal and a slow tactile signal indicatingnot to walk.

When the WALK light comes on, the CHANGE tone sounds once to attractattention and then the WALK tone is repeated eight times per second. Thedifference in tone and repetition rate gives the audible WALK signalwhile the high level tone acts as the tactile component with therepetition rate being the determining factor.

Various modifications may be made in details of design and constructionwithout departing from the scope and ambit of the invention.

We claim:
 1. An audio-tactile pedestrian push-button signalling systemcomprising signal generator means having an automatic gain controlcircuit, a transducer operative under the control of the signalgenerator means to produce predetermined audio and tactile signals,means for adapting said transducer to act as a responsive microphone soas to provide a feedback signal to said automatic gain control circuitfor adjusting a signal-to-noise level ratio of said system with respectto ambient traffic noise and powering said system by a single line froma remote power supply, said single line carrying a power signal whichalternates between at least first and second modes in response to the"WALK"/"DON'T WALK" status of an associated conventional pedestriansignalling system.
 2. A signalling system as set forth in claim 1 andfurther including a timing network responsive to said first and secondmodes of said power signal to actuate said signal generator means toprovide WALK, CHANGE and DON'T WALK audio tones and tactile signals in apredetermined sequence.
 3. A signalling system as set forth in claim 2and further including a power amplifier coupling said signal generatormeans to said generator.
 4. A signalling system according to any one ofclaims 2 or 3 and including a power supply circuit connected betweensaid single line and said signal generator means and operative to decodesaid first and second modes of said power signal to provide WALK andDON'T WALK signals to said timing network.
 5. A signalling system as setforth in claim 4 wherein said first mode is half-wave waveform of saidpower signal and said second mode is a full-wave waveform of said powersignal.
 6. A signalling system as set forth in claim 3 and includingmeans to limit the operation of said transducer as a microphone to timesbetween pulses of said DON'T WALK tone.
 7. A signalling system as setforth in claim 2 wherein said signal generator means is responsive tosaid timing network to provide during the generation of said DON'T WALKtone a low-frequency signal which is repeated on a regular basisfollowed by said DON'T WALK tone so as to provide an audible locatingtone and a tactile signal.
 8. A signalling system according to claim 7wherein said signal generator means provides said CHANGE tone when saidfirst mode is generated by said power signal, followed by said WALK tonerepeated on a regular basis, thereby creating both audible and tactilesignals.
 9. A signalling system as set forth in claim 1 wherein saidtransducer is coupled to said signal generating means through anamplifier rectifier.
 10. An audio-tactile pedestrian push-buttonsignalling system comprising the following:signal generating meansgenerating signals of at least first and second frequencies; a unitarytransducer element responsive to said signal generator means forfunctioning as a speaker to create (1) an audio signal in response tosaid signal of said first frequency and (2) tactile signal in responseto said signal of said second frequency; first means for detecting anambient noise level and adjusting said signal generating means inresponse thereto so as to ensure said audio signal may be heard by blindpedestrians; and a timing network for controlling the application ofsaid at least first and second frequencies to said transducer elementand including second means for disabling said unitary transducer elementfrom responding to said signal generator means so as to allow saidtransducer element to function as a microphone to convert ambient noiseto electrical signals for said first means such that said speaker andmicrophone functions of said unitary transducer element are timeinterleaved.
 11. A signalling system as set forth in claim 10 includingmeans responsive to a bi-state signal from a traffic control mechanismfor synchronizing said timing network with said traffic controlmechanism.
 12. A signalling system as set forth in claim 11 wherein saidsignal generator means includes means responsive to said timing networkfor providing a first signal mode to said unitary transducer elementindicative of an audio WALK signal and a second signal mode to saidunitary transducer indicative of an audio DON'T WALK signal.
 13. Asignalling system as set forth in claim 12 including means coupling saiddisabling means and said timing means such that said disabling means andsaid timing means cooperate to cause said unitary transducer element tofunction as a microphone between pulses comprising said second signalmode.
 14. A signalling system as set forth in claim 13 wherein saidfirst signal mode is a half-wave signal and said second signal mode is afull-wave signal.
 15. A signalling system as set forth in claim 13wherein said second signal mode includes a signal for vibrating saidunitary transducer element in a manner which provides a tactile signal.16. A signalling system as set forth in claim 15 wherein said firstsignal mode causes said unitary transducer element to generate a CHANGEtone to attract the attention of said blind pedestrian followed by aWALK signal repeated a predetermined number of times per second so as tocreate a tactile signal at said unitary transducer element.
 17. Asignalling system as set forth in claim 10 wherein said detecting meansis an amplifier rectifier responsive to said timing network to providean automatic gain control signal to said signal generator means inresponsive to said electrical signals from said unitary transducerelement.
 18. A signalling system as set forth in claim 10 including acoupling between said system and a conventional pedestrian signallingsystem which is comprised of a single line that serves both as a powersource and as a means to synchronize the operation of said two systems.19. A signalling system as set forth in claim 10 wherein said disablingmeans includes a power amplifier coupling said signal generator means tosaid unitary transducer element.